An air conditioner is mainly constructed of an outdoor unit that has a compressor and a heat exchanger, and an indoor unit that has a centrifugal fan and a heat exchanger. The indoor unit can be any one of a variety of types, such as one mounted on a wall, built into a ceiling, hanging from the ceiling or the like.
Indoor units that are built into or hanging from a ceiling are primarily composed of a casing that has an air suction port and a air discharge port on the bottom surface thereof, a centrifugal fan disposed inside the casing, and a heat exchanger disposed such that it surrounds the centrifugal fan. In this type of indoor unit, indoor air is taken into the interior of the casing from the air suction port, and is then blown by the centrifugal fan to the outer circumferential portion thereof. Then, the air blown to the outer circumferential portion of the centrifugal fan exchanges heat with the heat exchanger disposed around the centrifugal fan, and is then supplied to the interior of the room from the air discharge port.
Conventionally, many heat exchangers disposed in the casing of an indoor unit are cross fin type, and are bent into an approximate rectangular or circular shape such that they surround the centrifugal fan in a plane view.
With this type of heat exchanger, it is desirable to increase the effective length of the heat exchanger and to improve the heat exchanging performance of the air conditioner.
The size of the casing of the indoor unit can be made larger in order to increase the effective length of the heat exchanger. However, from a practical point of view, it is not desirable for the size of a conventional casing to be enlarged, and this is the main cause of an increase in costs.